1. Field of the Invention
The present invention relates to improvements in precision cutting tools, particularly high velocity cutting tool holders having indexable inserts or cutting bits.
2. Brief Description of the Prior Art
Precision cutting tools that utilize indexable inserts or cutting bits are known in the prior art. Tools of this type, currently in extensive commerical use are disclosed in my U.S. Pat. No. 3,237,275 granted Mar. 1, 1966, the disclosure of which patent, by reference, is incorporated herein. Other patents disclosing tool holders for various purposes and having detachable or throwaway cutting bits are British Pat. No. 874,114 and U.S. Pat. Nos. 2,378,094, Nunez-Vaz, 2,521,868, Otto, 2,561,470, Hadley et al., 2,645,844, Longe, 3,050,828, Cashman et al., 3,662,444, Erkfritz, 3,818,562, Lacey, 4,182,587, Striegl, 4,182,587 and 4,194,860, Hopkins.
While the prior art cutting tools having indexable inserts have provided many advantages in high velocity cutting tools including superior cutting materials and reduced maintenance costs, they have, in common, a disadvantage of being unable to withstand to a degree that is economically desirable the extreme abuse and shock to which they are subjected in certain industrial applications, for example, the harvesting of trees and the processing of lumber. As a result, in such applications deterioration is rapid. The tool mortality rate is high, requiring frequent replacement not only of the indexable insert but also of the entire tool.
In recent years it has become extremely important in the harvesting of trees and the processing of lumber to focus greater attention on the improvement of profitability in the machining of smaller logs and the gaining of greater monetary recovery from wood chips that are formed in the process. Chip quality, consistency of size within certain parameters, is determined by rate of feed, comparative freedom from cutter clamp and holder interference during cutting and the cutting geometry employed. Chip monetary value has been found to be commensurate with size and shape of the chips produced.
In view of these considerations, and particularly, the impact thereon of excessive tool expense resulting from their high mortality rate, there has arisen a need for further improvements in the cutting tool art for lowering the rate of tool deterioration, and upon such deterioration, for facilitating the necessary replacement and confining the replacement to the damaged area. Additionally, there has arisen a need for further improvements in order to effect smoother cutting, more accurately cut surfaces, and consistency in size and shape of chips produced.